1. Field of the Invention
The invention is directed to a crane, particularly a railway crane, with a superstructure arranged on an undercarriage so as to be swivelable around a vertical axis, a jib, and a counterweight arranged on the superstructure so as to be movable as a function of swiveling movement of the superstructure.
2. Description of the Prior Art
A revolving jib crane with a chassis or undercarriage and a superstructure arranged on the latter so as to be swivelable is known from DE 224 303 A1. The boom or jib is supported at the superstructure. Furthermore, a counterweight is arranged at the side of the superstructure remote of the jib. The counterweight is constructed so as to be displaceable in the horizontal direction in extension of the jib as seen from the top in order to change the counterweight moment. The counterweight is adjusted as a function of the swiveling movement of the superstructure. For this purpose, the counterweight is mechanically coupled with the rotating drive for the superstructure via a lever system and a toothed wheel.
The movability of the counterweight has proven disadvantageous since it increases the working radius or length of the superstructure in the rear, i.e. the distance between the swivel axis of the superstructure and the outer contour of the counterweight remote of the swivel axis. Although this increased length results in an increase in the counterweight moment and accordingly in the load carrying capacity of the crane, it is impossible to use the crane in confined spaces. A jib crane constructed as a railway crane will serve as example. Its working range is frequently limited at least on one side by a prescribed clearance gauge. The increased length renders it almost impossible to swivel this crane on a track running alongside a parallel track, since the counterweight exceeds the clearance gauge laterally in the direction of the neighboring track already at a small swiveling angle and this neighboring track must accordingly be barred to traffic.